#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int i = 0;
	double sum = 0;
	int f = 1;
	for (i = 1; i <= 100; i++)
	{
		sum += f * 1.0/i;
		f = -f;
	}
	printf("%  lf", sum);
	return 0;
}